Well, finally after the latest 15.10 release and Linux 4.2.0 kernel updates in Ubuntu, my ACPI buttons (Fn + F2/F3) are fixed and can change my screen brightness natively (I was previously using hacky stuffs using macro like commands and binded them to F2/F3). But earlier, I installed GNOME desktop which initially caused my desktop to be black and very slow, that I already fixed by changing from gdm to lightdm and then back to gdm as suggested here in AskUbuntu. Now, I can't change my screen brightness using Fn + F2/F3 keys and also it don't work when changing in the GNOME menu or even in the Settings (which all worked when I was in Unity).

If there is anything I need to provide like logs or any useful info, I will gladly give them. Thanks for your help.

EDIT: As an added note, it is unusual, but Fn+F2/F3 triggers the notification of changing the brightness and it goes up/down but the screen brightness itself is unaffected.

1 Answer 1


Apparently, it looks like gdm or GNOME Desktop itself didn't like the acpi_backlight=vendor line in my /etc/default/grub file. As a side effect, an error about fnfxd.service failing to start appears at boot. I guess that when I switch back to Unity, Fn+F2/F3 keys will not work. But as long as I am in GNOME, I guess this little bit of dirty workaround would do. If there will be someone who can give a better working answer, I'll mark you as the accepted answer. Thanks!

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